The present invention relates generally to battery pack assembly and specifically to a method to ensure full functionality of a battery pack using thermal imaging.
The need to reduce fossil fuel consumption and emissions in automobiles and other vehicles predominantly powered by internal combustion engines (ICEs) is well known. Vehicles powered by electric motors attempt to address these needs. Another alternative solution is to combine a smaller ICE with electric motors into one vehicle.
Such vehicles combine the advantages of an ICE vehicle and an electric vehicle and are typically called hybrid electric vehicles (HEVs). See generally, U.S. Pat. No. 5,343,970 to Severinsky.
The HEV is described in a variety of configurations. Many HEV patents disclose systems where an operator is required to select between electric and internal combustion operation. In other configurations, the electric motor drives one set of wheels and the ICE drives a different set.
Other, more useful, configurations have developed. For example, a series hybrid electric vehicle (SHEV) configuration is a vehicle with an engine (most typically an ICE) connected to an electric motor called a generator. The generator, in turn, provides electricity to a battery pack and another motor, called a traction motor. In the SHEV, the traction motor is the sole source of wheel torque. There is no mechanical connection between the engine and the drive wheels. A parallel hybrid electrical vehicle (PHEV) configuration has an engine (most typically an ICE) and an electric motor that work together in varying degrees to provide the necessary wheel torque to drive the vehicle. Additionally, in the PHEV configuration, the motor can be used as a generator to charge the battery pack from the power produced by the ICE.
A parallel/series hybrid electric vehicle (PSHEV) has characteristics of both PHEV and SHEV configurations and is sometimes referred to as a xe2x80x9cpowersplitxe2x80x9d configuration. in one of several types of PSHEV configurations, the ICE is mechanically coupled to two electric motors in a planetary gear-set transaxle. A first electric motor, the generator, is connected to a sun gear. The ICE is connected to a carrier. A second electric motor, a traction motor, is connected to a ring (output) gear via additional gearing in a transaxle. Engine torque can power the generator to charge the battery pack. The generator can also contribute to the necessary wheel (output shaft) torque if the system has a one-way clutch. The traction motor is used to contribute wheel torque and to recover braking energy to charge the battery pack. In this configuration, the generator can selectively provide a reaction torque that may be used to control engine speed. in fact , the engine, generator motor and traction motor can provide a continuous variable transmission (CVT) effect. Further, the HEV presents an opportunity to better control engine idle speed over conventional vehicles by using the generator to control engine speed.
The desirability of combining an ICE with electric motors is clear. There is great potential for reducing vehicle fuel consumption and emissions with no appreciable loss of vehicle performance or driveability. The HEV allows the use of smaller engines, regenerative braking, electric boost , and even operating the vehicle with the engine shutdown. Nevertheless, new ways must be developed to optimize the HEV""s potential benefits.
One such area of HEV development is ensuring full functionality of battery packs used to power the electric traction motor. The battery pack for an HEV typically produces from around 216 to 385 volts, with 6.5 amp-hours nominal capacity, and approximately 36 to 40 kW of power. Since electric powered vehicles require such high voltage and large current capacity, HEV battery packs generally combine a number of interconnected individual batteries. To ease assembly of battery pack s and to reduce battery pack cost, a standard battery size is generally used. For example, one possible battery pack could be assembled in two sections with each section having twenty individual modules. Unfortunately, during the assembly of these battery modules into battery sections, loose connections can occur resulting in high impedance on both charge and discharge as well as recording strange open circuit voltages. Unresolved, these faulty connections can cause poor vehicle performance, extended service time, warranty costs, and customer dissatisfaction.
Battery testing is certainly known in the prior art. Standard discharge rates tests on battery packs can show a severe voltage drop or unexplained voltage readings if loose or faulty connections are present. Since the source of the unexplained voltage variance is not identified during this type of test, unnecessary delays in test time result while the problem is located. Therefore, a fast and efficient method and system to ensure battery pack assembly functionality is necessary.
Accordingly, the present invention provides a method and system to quickly and efficiently verify full functionality of a battery pack assembly. Specifically, the present invention ensures full functionality using thermal imaging of a battery pack having at least two battery modules, the battery modules having electrode terminals combined to form a battery section. The battery modules are combined by a first set of connectors between an electrode terminal of one battery module to an electrode terminal of another battery module. A system using a first thermal image scan of the battery section during a first power discharge test determines whether the connections among the battery modules are within a first predetermined temperature tolerance. If any modules are not within the tolerance, the battery section is pulled from assembly, fixed and returned to assembly. The battery sections are combined to form a battery pack using a second set of connectors which connect a terminal of one battery section to a terminal of another battery section. Next, a system using a second thermal image scan of the battery pack during a second power discharge test determines whether the connections among the battery sections are within a second predetermined temperature tolerance and fixes them.
The present invention can also include a comparison of voltage among the battery pack and each battery section and a means to adjust any battery pack that exceeds a predetermined voltage variation.
The present invention works for battery packs wherein the battery modules are combined in either series or parallel configuration. The thermal image scan comprises a means to obtain thermal radiation variation using infrared intensity data.
The infrared intensity data can be digitized and processed so that infrared intensity values are assigned color values and put on a visual display.
Advantages of the present invention can include efficient developmental costs in that existing technologies can be used and that waste is reduced since battery sections that failed their initial testing can be fixed and reused.